The present invention relates to the field of earth moving equipment and more particularly to a system for quick and accurate connection and disconnection of earth moving equipment and a tractor.
A basic hitch connection, used since the early 1950""s, consists of a yoke arrangement and a drawbar especially made to accept the horizontal pin used to connect a scraper or other earth moving equipment to a towing tractor. The drawbar consists of a steel bar fastened to the belly of the towing tractor and fitted with two or four ears at the rear of the tractor. Each of the ears includes a hole. The rear portion of the drawbar is supported by a cross member in the tractor frame or an added cross member.
The drawbar and yoke hitch provide a flexible connection between the scraper and tractor. This hitch arrangement has been accepted by most manufacturers and is pervasive in the industry.
This design allows the vertical load of the scraper to be placed as far forward as possible to reduce the effect of raising the tractor front, while keeping the vertical pivot point as far away as possible from the tires to allow full turns. The yoke assembly provides a hinge between the tractor and scraper and lets the scraper rock from side to side over uneven ground. Side travel is limited to 30 degrees due to the arrangement of the yoke halves.
Connection of the scraper to a tractor is accomplished by positioning the tractor at the correct distance and angle to allow installation of a horizontal pin through both the drawbar ears and the scraper hitch. This process requires a xe2x80x9cspotterxe2x80x9d to direct the tractor driver into position and, when properly positioned, to attempt to install the pin connecting the scraper and tractor by passage of the pin through a series of aligned holes of the drawbar ears and the scraper hitch. This exposes the xe2x80x9cspotterxe2x80x9d to danger since they must be in the critical zone between the moving tractor and the stationary scraper.
The drawbar pin is a steel shaft with a head welded on one end and threads and a nut on the opposite end. Installation of the pin is not easy since the alignment of the holes of the drawbar ears and the scraper hitch is imprecise, and usually requires the use of a large hammer to drive the pin into place. This may result in damage to the pin, drawbar, or yoke hitch.
The new quick hitch drawbar assembly of the present invention accepts a standard yoke hitch but simplifies the tractor/scraper connection. Holes in the drawbar are replaced with slots which are angled away from the scraper and toward the rear of the tractor to prevent accidental disconnection. These slots are wider at the top to simplify alignment of the yoke pin down into the slots to seat the yoke pin in a pin cradle. The forward portion of the drawbar ears are raised to form a stop for the horizontal pin when positioning the tractor.
The tractors""s hydraulic system is used to raise or lower the scraper to the correct height for connection. The tractor is backed into the scraper yoke hitch where the raised portions of the drawbar ears and locking or latching cam are contacted. The scraper hydraulics, connected to the hydraulic system of the tractor, are then used to lower the scraper into the drawbar slots.
Once the hitch pin is bottomed in the drawbar slots, the locking cams are manually rotated by a removable actuating lever to a locking position to latch the yoke pin in place. A cam pivot pin is situated to prevent accidental hitch disconnection.
The locking cams are retained in position by their weight and two spring loaded ball screws engaging dimples in detents located in the sides of the locking cams. Further, there are physical stops to prevent the cams from traveling past the dimples and causing the ball screws from losing their frictional connection on the cam.
The pivot pin for the latching cams has two notches/grooves located at the edges of the cams. The purpose of these are to provide a xe2x80x9cbreakawayxe2x80x9d point, preventing a rollover of the scraper. The size and depth of the notches allows the cam pin to break as a result of excessive forces, releasing the cams and allowing the scraper to separate from the tractor, therefore preventing a rollover.
Accordingly, it is an object of the present invention to provide a drawbar assembly having a plurality of slotted ears which guide a yoke pin down into a pin cradle.
It is another object of the present invention to provide a drawbar assembly having a plurality of slotted ears which guide a yoke pin down into a pin cradle and having pivotally mounted locking cams rotatable into the path of the slotted ears to engage and retain the yoke pin at the bottom of the pin cradle.
It is still yet another object of the present invention to provide a drawbar assembly having a plurality of slotted ears which guide a yoke pin down into a pin cradle and having pivotally mounted locking cams rotatable into the path of the slotted ears to engage and retain the yoke pin at the bottom of the pin cradle, the locking cams having side grooves engaged by a biased pin in detents at opposite ends of the side grooves for guiding and maintaining the locking cams between a locked and an unlocked position.
It is still yet another object of the present invention to provide a drawbar assembly having a plurality of slotted ears which guide a yoke pin down into a pin cradle and having pivotally mounted locking cams rotatable into the path of the slotted ears to engage and retain the yoke pin at the bottom of the pin cradle, the locking cams having side grooves engaged by a biased pin in detents at opposite ends of the side grooves for guiding and maintaining the locking cams between a locked position and an unlocked position, the locking cams having a removable cams actuating lever for rotation of the locking cam through approximately 180 degrees of motion.